1. Field of the Invention
The present invention relates to thin film type magnetic transducer heads in electromagnetic induction type or magnetoresistance effect type, and more particularly to a thin film type magnetic transducer head used in reproduction of a digital magnetic recording.
2. Description of the Prior Art
Referring to FIG. 1, a thin film type magnetic transducer head, for example, that of electromagnetic induction type, comprises a magnetic substrate 1 of Mn-Zn ferrite, a conductive layer 3 as a head winding formed on the magnetic substrate 1 through an insulation layer 2 of SiO.sub.2 or Si.sub.3 N.sub.4, and a magnetic core 5 of permalloy or sendust formed on the conductive layer 3 also through an insulation layer 4 of SiO.sub.2 or Si.sub.3 N.sub.4 so as to cross the conductive layer 3. Front end of the magnetic core 5 extends to an opposite surface 6 to be faced to a travelling magnetic recording medium, and a gap spacer layer 7 of SiO.sub.2 having a prescribed thickness is interposed between the front end of the core 5 and the magnetic substrate 1 and further an effective magnetic gap g with gap length specified by the thickness of the gap spacer layer 7 is faced to the opposite surface 6 to the travelling magnetic recording medium. Rear end of the magnetic core 5 is attached to the magnetic substrate 1 directly, for example, and magnetically connected to the substrate 1 in close connection. Thus the magnetic circuit of the substrate 1 - the magnetic gap g - the magnetic core 5 - the substrate 1 is formed around the conductive layer 3, and signal magnetic flux from the travelling magnetic recording medium faced to the opposite surface 6 is supplied to the magnetic circuit through the effective magnetic gap g, thereby induction current is produced in the conductive layer 3 being head winding so as to take the reproduction signal.
Referring to FIG. 2, the thin film type magnetic transducer head has the effective magnetic gap g as shown schematically. Since the core length at one core front side opposed through the gap g of the magnetic circuit is specified by the thickness of the magnetic core 5, the core length is as short as 0.1-10 .mu.m and the frequency characteristics are affected by the shape effect. Although the intrinsic frequency characteristic curve decreases simply as shown in broken line of FIG. 3 on account of spacing loss, a real characteristic curve has weaving as shown in solid line of FIG. 3. FIG. 4 shows deviation of the weaving, where frequencies at apexes of the first dip, the second peak, the second dip, . . . are designated by f.sub.1, f.sub.2, f.sub.3, . . . respectively, intersections of the weaving at both sides of the dips and the peaks with the convergence level axis (deviation 0) are taken as f.sub.o, f.sub.a, f.sub.b, f.sub.c, and wave lengths corresponding to these frequencies are taken as .lambda..sub.1, .lambda..sub.2, .lambda..sub.3 ; .lambda..sub.opl , .lambda..sub.a, .lambda..sub.b, .lambda..sub.c. Each wave length is a value of the relative velocity v of the travelling magnetic recording medium to the magnetic transducer head divided by each frequency.
Since the weaving in the frequency characteristics is phenomenon caused by that the core length is short in the thin film type magnetic transducer head, this phenomenon occurs irrespective of the detecting mode in the thin film type magnetic head, either electromagnetic induction type or magnetoresistance effect type.